Efficacy and safety of long-term treatment with lenalidomide and dexamethasone in patients with relapsed/refractory multiple myeloma

Data from two randomized pivotal, phase 3 trials evaluating the combination of lenalidomide and dexamethasone in relapsed/refractory multiple myeloma (RRMM) were pooled to characterize the subset of patients who achieved long-term benefit of therapy (progression-free survival >= 3 years). Patients with long-term benefit of therapy (n = 45) had a median duration of treatment of 48.1 months and a response rate of 100%. Humoral improvement (uninvolved immunoglobulin A) was more common in patients with long-term benefit of therapy (79% vs 55%; P = 0.002). Significant predictors of long-term benefit of therapy in multivariate analysis were age <65 years (P = 0.03), beta 2-microglobulin <2.5 mg/l (P = 0.002) and fewer prior therapies (P = 0.002). The exposure-adjusted incidence rate (EAIR) of grade 3-4 neutropenia was lower in patients with long-term benefit of therapy (13.9 vs 38.2 per 100 patient-years). The EAIR for invasive second primary malignancy was the same in patients with long-term benefit of therapy and other patients (1.7 per 100 patient-years). These findings indicate that patients with RRMM can experience long-term benefit with lenalidomide and dexamethasone treatment with manageable side effects.